A population disease transmission dynamics describing the susceptibility of hard clam Meretrix lusoria to Hg-stressed birnavirus
Date Issued
2007
Date
2007
Author(s)
Yeh, Ching-Hung
DOI
zh-TW
Abstract
The purpose of this thesis is to assess the susceptibility of hard clam (Meretrix lusoria) populations exposed to mercury (Hg)-stressed birnavirus by integrating nonlinear epidemiological dynamics of host–pathogen relationships into a stage-structured matrix population model. Dynamic energy budget (DEBtox) theory links bioenergetics-based growth model to enhance toxicity assessments of Hg and describe the growth probability of toxicity inhibition distinguish from three modes of toxic action (MOA). For estimating survival probability, this study employs damage assessment model (DAM)-based Hill model to assess the relationship between internal burden concentration and mortality. Fecundity rate is related to weight-varied which is calculated from power function. Vital rate can be evaluated among growth, survival, and fecundity rate, population growth rate (λ) and population dynamics of hard clam exposed to Hg-stressed can be further estimated. Moreover, stressor-specific transmission rate, mortality rate from disease-induced susceptible-infectious-mortality (SIM) model are estimated to evaluate basic reproductive number (R0) which is defined as the average number of secondary cases generated by one primary infected case. Two kinds of disease challenge experiments of virus + Hg and Hg + virus are considered to assess the susceptibility of hard clam exposed to Hg-stressed birnavirus. The results show λ > 1 within 10 μg Hg L-1, however, hard clam populations will decreased when exposed to > 30 μg Hg L-1. The effect concentration causing 50 % reduction (ER50) is estimated to be 12.07 μg L-1 after a 1-year simulation, by which hard clam populations harvest controlling can be pre-analyzed. The results considering the processes of stage-specific disease transmission also indicate that clam populations will decreased to 60 % for virus + 5 μg L-1 and 80 % for 5 μg L-1+ virus within 20 days. On the other hand, when transmission rates reduced to 0.4 and 0.2 fold for virus + 5 μg L-1 and 5 μg L-1+ virus, respectively, the disease outbreak can be totally contained. Moreover, this study presents a simple and mechanistic-based model to effectively assess the susceptibility of hard clam exposed to Hg-stressed birnavirus. The results indicate that hard clam populations less than 400 ind m-2 can be allowed to control outbreak. It is confident that the model can be easily adapted for other aquaculture species to assess chemical-stressed pathogen.
Subjects
汞
族群動態
矩陣族群模式
疾病傳輸
易感性
Hard clam
Meretrix lusoria
Mercury
Population dynamic
Matrix population model
Disease tranmission
Susceptibility
Type
thesis
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